byuu says:
Changelog:
- new md/bus/ module for bus reads/writes
- abstracts byte/word accesses wherever possible (everything but
RAM; forces all but I/O to word, I/O to byte)
- holds the system RAM since that's technically not part of the
CPU anyway
- added md/controller and md/system/peripherals
- added emulation of gamepads
- added stub PSG audio output (silent) to cap the framerate at 60fps
with audio sync enabled
- fixed VSRAM reads for plane vertical scrolling (two bugs here: add
instead of sub; interlave plane A/B)
- mask nametable read offsets (can't exceed 8192-byte nametables
apparently)
- emulated VRAM/VSRAM/CRAM reads from VDP data port
- fixed sprite width/height size calculations
- added partial emulation of 40-tile per scanline limitation (enough
to fix Sonic's title screen)
- fixed off-by-one sprite range testing
- fixed sprite tile indexing
- Vblank happens at Y=224 with overscan disabled
- unsure what happens when you toggle it between Y=224 and Y=240
... probably bad things
- fixed reading of address register for ADDA, CMPA, SUBA
- fixed sign extension for MOVEA effect address reads
- updated MOVEM to increment the read addresses (but not writeback)
for (aN) mode
With all of that out of the way, we finally have Sonic the Hedgehog
(fully?) playable. I played to stage 1-2 and through the special stage,
at least. EDIT: yeah, we probably need HIRQs for Labyrinth Zone.
Not much else works, of course. Most games hang waiting on the Z80, and
those that don't (like Altered Beast) are still royally screwed. Tons of
features still missing; including all of the Z80/PSG/YM2612.
A note on the perihperals this time around: the Mega Drive EXT port is
basically identical to the regular controller ports. So unlike with the
Famicom and Super Famicom, I'm inheriting the exension port from the
controller class.
byuu says:
Changelog:
- 68K: MOVEQ is 8-bit signed
- 68K: disassembler was print EOR for OR instructions
- 68K: address/program-counter indexed mode had the signed-word/long
bit backward
- 68K: ADDQ/SUBQ #n,aN always works in long mode; regardless of size
- 68K→VDP DMA needs to use `mode.bit(0)<<22|dmaSource`; increment by
one instead of two
- Z80: added registers and initial two instructions
- MS: hooked up enough to load and start running games
- Sonic the Hedgehog can execute exactly one instruction... whoo.
byuu says:
All of the above fixes, plus I added all 24 variations on the shift
opcodes, plus SUBQ, plus fixes to the BCC instruction.
I can now run 851,767 instructions into Sonic the Hedgehog before hitting
an unimplemented instruction (SUB).
The 68K core is probably only ~35% complete, and yet it's already within
4KiB of being the largest CPU core, code size wise, in all of higan. Fuck
this chip.
byuu says:
I split the Register class and read/write handlers into DataRegister and
AddressRegister, given that they have different behaviors on byte/word
accesses (data tends to preserve the upper bits; address tends to
sign-extend things.)
I expanded EA to EffectiveAddress. No sense in abbreviating things
to death.
I've now implemented 26 instructions. But the new ones are just all the
stupid from/to ccr/sr instructions.
Ryphecha confirmed that you can't set the undefined bits, so I don't
think the BitField concept is appropriate for the CCR/SR. Instead, I'm
just storing direct flags and have (read,write)(CCR,SR) instead. This
isn't like the 65816 where you have subroutines that push and pop the
flag register. It's much more common to access individual flags. Doesn't
match the consistency angle of the other CPU cores, but ... I think this
is the right thing to for the 68K specifically.
Tim Allen